Oxide semiconductor thin film field-effect transistors shall be a hot spot in the field of display in the future and have been researched and developed widely in recent years. A 2T1C structure serves as the most basic structure of an active matrix organic light-emitting diode (AMOLED) based on a thin film field-effect transistor and is composed of two thin film field-effect transistors and a storage capacitor Cst arranged between the two thin film field-effect transistors, as shown in FIG. 1.
Mobility of an amorphous indium-gallium-zinc oxide (a-IGZO) film serving as an active channel layer can reach 80 cm2/Vs (while the mobility of amorphous silicon is merely 0.5˜0.8 cm2/Vs). Further, the procedure of manufacturing amorphous indium-gallium-zinc oxide (a-IGZO) film is compatible with the procedure of manufacturing amorphous silicon (a-Si). Therefore, indium-gallium-zinc oxide (IGZO) has potential application in the organic light-emitting diode (OLED) of next generation.
In the prior art, an IGZO-TFT (indium-gallium-zinc oxide thin film transistor)-based 2T1C structure comprises a switching thin film field-effect transistor, a driving thin film field-effect transistor, and a storage capacitor connecting the switching thin film field-effect transistor and the driving thin film field-effect transistor. The switching thin film field-effect transistor plays a role of a switch, and the driving thin film field-effect transistor plays a role of a regulating a gray scale of an OLED. Under an ideal condition, different thin film field-effect transistors have different electric requirements. As shown in FIG. 2, an switching thin film field-effect transistor requires a small sub-threshold swing (SS) of a transfer characteristic curve (IdVg curve) thereof, so that the switching thin film field-effect transistor can be switched on/off quickly. As shown in FIG. 3, a driving thin film field-effect transistor requires a large sub-threshold swing of the transfer characteristic curve thereof, so that a gray scale of an OLED can be regulated slowly through the driving thin film field-effect transistor.
However, in the prior art, in a 2T1C structure, the sub-threshold swing of the transfer characteristic curve of the switching thin film field-effect transistor is almost identical with that of the driving thin film field-effect transistor because the structures of the switching thin film field-effect transistor and the driving thin film field-effect transistor are the same. Therefore, the 2T1C structure in the prior art does not have both of the functions of switching on/off the switching thin film field-effect transistor quickly and regulating the gray scale of the OLED slowly through the driving thin film field-effect transistor.